1. Field of the Invention
The present invention relates generally to glass laser amplifier structures, and more particularly pertains to a glass bead laser amplifier with a phase conjugate mirror which is designed to operate at relatively high optical powers. The glass bead laser amplifier of the subject invention is designed to be easily manufactured and also to be scaled up in size to provide a relatively high optical power output.
2. Discussion of the Prior Art
The present invention is directed to high power glass laser amplifier structures. The repetition rates for high power pulsed glass laser amplifiers of the prior art are generally limited by the low heat dissipation rates of the glass laser materials during and following each laser pulse. This heat dissipation problem has essentially limited laser operations at reasonably high power levels. The removal of that portion of the pumping energy which is normally converted to heat in the glass laser material is a paramount problem in maintaining efficient operation of such high power glass laser devices. Liquid laser systems have been suggested as one approach in the prior art to overcoming the operational limitations imposed by such heat dissipation problems. However, while ameliorating the heat dissipation problems, the temperature gradients within the liquid laser medium produce refractive index gradients which grossly influence the optical quality of the laser cavity. Therefore a liquid laser amplifier system, while somewhat obviating the heat dissipation problems, introduces other more complex problems, and has not provided an acceptable approach for increasing the average operational power of such laser amplifier devices.
The present invention is directed to a high power glass bead laser amplifier which has excellent optical qualities and mechanical stability, while providing for adequate heat dissipation in a type of construction which is easily manufactured and scaled up in size to provide for a relatively high optical power output.
Glass lasers, particularly Nd glass lasers, are playing an increasingly important role in science and industry, both militarily and commercially. They are used in laser fusion, combustion and flow field diagnostics, medicine, nonlinear optics, cutting, welding and other technological areas where high peak powers and large pulse energies are required. Glass lasers are generally very scalable, that is they can be made relatively large because glass can be easily doped, polished, and made in sufficient quantities with good energy density storage for laser amplifiers.
Although glass lasers are scalable, the time average power of the laser will not scale indefinitely. This is due primarily to the time necessary to cool the glass rods or slabs of the amplifier. Glass, being a poor conductor of heat, prevents a rapid heat dissipation. Accordingly it is important to cool the glass during operation to prevent index of refraction gradients caused by temperature inhomogeneities. These gradients suppress lasing, increase the chance of laser damage due to focusing effects of the gradients, and cause poor laser beam quality. The cooling time also limits the duty cycle, thus decreasing the actual possible average power output of the glass laser.
Segmented doped glass lasers with cooling are well known in the art, as exemplified by Gudmundsen U.S. Pat. No. 3,487,330, Young U.S. Pat. No. 3,602,836, Cuff U.S. Pat. No. 3,628,179, Young 3,675,152, and Gans U.S. Pat. No. 3,735,282. Generally, these doped regular array of similarly shaped and aligned glass elements therein, such as a stacked disk design, and coolant is circulated around the regular array of glass elements to provide cooling therefor.
Moreover, the use of a phase conjugator reflector in association with a laser cavity to eliminate optical distortions introduced into a laser beam is also well known, as indicated by "APPLICATIONS OF OPTICAL PHASE CONJUCTION" Scientific American, January, 1986, and also by Pohl U.S. Pat. No. 3,617,927, Bret U.S. Pat. No. 3,999,144, Wang U.S. Pat. No. 4,005,935, Wang et al. U.S. Pat. No. 4,233,571 and Evtuhov U.S. Pat. No. 4,321,550
The present inventing distinguishes from all of the above cited prior art by recognizing that a phase conjugator reflector can be used with a glass laser in such a manner as to make the fabrication and assembly of the glass laser relatively simple and economical, and also to allow the glass laser to be easily scaled up in size to provide relatively high optical power output beams.